Phased array antennas are used to transmit and receive high gain, narrow beam, radio (RF) signals for communications and radar. Each antenna element of the array is fed with an RF path. The RF paths are combined together using an RF combiner network. To steer each beam, each transmit path and receive path includes one or more phase shifters and adjustable gain amplifiers. However, each phase shifter and amplifier must be controlled individually with calibrated values to direct the beam. Therefore, a large number of control signals are required for controlling each element of an array. This increases both the complexity and the cost of a printed circuit board in order to handle the large number of required control traces.
The typical control bus of a phased antenna array comprises a Clock line, a Data In line, a Data Out line, a Latch line, a Reset line, a transmit (TX) Enable line, and a receive (RX) Enable line. These control signals must be routed to every transmit/receive element of an array. The high-speed control signals (e.g., Clock, Data) are typically routed as differential pairs, which doubles the number of traces to be routed and adds routing constraints to control trace impedances. These signals require some level of noise immunity to protect the signals from noise sources within the printed circuit board. For example, the RF power ramp on/off and RF pulses may create detrimental transients in the control bus. If a single element is defective, it has the potential of disabling other elements. Reducing the large number of control signals would simplify the printed circuit board construction. This would reduce product development time and improve flexibility for implementing an RF array into different platforms.
Therefore, there is a need in the art for an improved RF phased antenna array. In particular, there is a need for an improved control interface for controlling multiple transmit/receive (TX/RX) elements of a phased antenna array.